Radio tube shield



Aug. 11, 1936. F. HAFECOST ET AL RADIO TUBE SHIELD Filed Feb. 9, 1935 Patented Aug. 11, 1936 UNITED STATES PATENT OFFICE 7 2,050,885 RADIO TUBE SHIELD Frederick Hafecost, Brooklyn, and Edward F. Staver, Jackson Heights, N. Y., assignors to Goat Radio Tube Parts, Inc-., Brooklyn, N. Y., a corporation of New York Application February 9, 1935, Serial No. 5,690 7 Claims. (01. 250-275) This invention relates to a radio tube shield, in particular) the form-fitting tube assembly and more particularly to a form-fitting shieldof shown therein. comprises a plurality, in this case the removable type. two, substantially symmetrical parts or halves I It is common practice to electrostatically shield and 2 formed from sheet metal and adapted to be the tubes in the modern radio receiving sets. One held in position by resilient means, in this case a 5 form of shield employed is the so-called can split clamping ring 3 which is normally seated in shield which as the term implies is merely a metal a circumferentially formed groove 5. The position can inverted over the tube so that the opened of the groove 4 may vary, but in the present inend seats on the chassis and completely encloses stance is slightly below the maximum diameter the tube. This type of shielding is effective but of the-bulb 5 of the tube and the clamping ring. 3 10 is extravagent of chassis space and does not al-- is made of suitable spring wire and has a diameter ways permit the positioning of the tubes to suit slightly less than the outside diameter of the the set manuiacturers requirements. shieldv at the point of engagement therewith, so A certain form-fitting tube shield now on the that when the ring 1 pp into e r ove 4 market overcoming these objections to the can the ends thereof are slightly separated, thus in.- 15 shield, comprises two symmetrically paired parts suring the te of the ring being exerted of sheet metal and shaped to fit closely to the hold the two halves or sections of the shield firmly bulb of the tube, said parts being held in place together when assembled. The longitudinal edges by a clamping ring. The length of the dished of each of the half sections l and 2 are flanged metal parts is substantially equal to the length of outwardly and are of suflicient area as to form a 20 the tube to be housed therein when measured substantial abutting surface when the two halves. along the tube axis, but not ofsufiicient length to are positioned so. as to oppose each other. completely house the customary electrode sealed. As will be observed from the drawing the genin the end of the bulb-and provided with a metallic eralv inner; contour of each half part of the shield topcap. With the-topcapexposed or unshielded; is substantially that of the outer contour of the 25 the tubemay be subject to external electrical'distube. The lower end of the shield members I and turbances, which render'the shielding correspond- 2 are semi-cylindrical in shape and together form ingly imperfect. a cylindrical extension which substantially covers It is an object of the present invention to prothe base of the tube. Immediately adjacent this vide a form-fitting shield adapted to enclose subextension the. shield members I and 2 taper up- 30 stantiallythe entire tube including the top cap; wardly, following thegeneral contour of the bulb. whereby improved electrostatic shielding is 0b: This taper increases upwardly until the parts I tained. and- 2 reach their largest radius at a point slightly It is another-object of the invention to provide abov t middle of the bulb T e pa t I a d a form-fitting shield having a simple mechanical 2 then taper or curve inwardly so as to fit around 35 expedient that compensates for slight variations the dome l2 of the bulb 5.

in the diameter of the bulbs of a given sizean'd/or The top portion of the shield members conshape of tube; also in imperfections injoiningthe verges inwardly so as to form a chimney 6 of bulb to the base of the tube, smaller diameter than that of the dome I2, 40 Other novel features of construction will maniwhich extends upwardly a distance sufficient to 40 fest themselves as the description proceeds; enclose the electrode-brought out the top of the Referring to the accompanying drawing: bulb 5 and covered: with a metal cap I. To pro- Fig. 1 is a partially sectioned view of the paired vide means for connecting a leading-in C d parts comprising the shield fitted to a radio tube; tor to the top cap 1 a suitable aperture 8 is formed Fig. 2 is an elevation of one of the paired parts in the chimney section 6. The top edge of the 45 of the shield as shown in Fig. 3; chimney portion 6 is turned or spun inwardly Fig. 3 is a perspective view-of the two halves of a short distance, but there remains a circular the'shield slightly separated, but illustrating the opening or cut-away portion which is of sufiimanner in which it is applied to a radio tube; cient diameter to remove any danger of elec- Fig. 4 is a fragmentary perspective view of the trical contact with the top cap 1. It also facili- 50 top part of one of the shield halves, showing a tates the attachment of the leading-in conductor modification; and without removing the shield when enclosing the Fig. 5 isa fragmentary perspective. View of an,- tube. other modified form of the shield assembly. In Figs. 2 and 3 of the drawing; the aperture 8 Referringto the accompanying drawing. (Fig.3 is centrally located with respect to the curved or cylindrical portion of one of the half shield mem-- bers. As will be noted the aperture 8 is U-shaped and runs from the perimetral edge of the shield member and continues downwardly a distance to insure good clearance with the leading-in conductor for the top cap F. When the aperture 8 is centrally located with respect to the chimney portion 6, the opposing half of the shield need not have a similar aperture, and consequently that section of the chimney is solid metal up to its perimetral edge. However, various modifications may be made with respect to the formation of the aperture 8. For example, the aperture may be formed so as to be equally divided between the adjacent longitudinal edges of each of the paired halves l and 2 of the shield (see Figs. 1 and 4) This form of construction makes in efifect a right and a left of the two halves comprising the shield.

A modification of the shield assembly is shown in Fig. 5 consisting of using the shield half 2 which is not provided with the aperture 8, and combining it with a half of the shield-forming parts that does not have the chimney extension. Such a combination effects economy in material and may be used where complete shielding is not necessary because of the particular location of the tube on a specific design of chassis.

The difierent types of radio tubes now on the market vary with respect to their length as well as diameter; also they vary with respect to the contour of the bulb. For example, there is the small dome type represented by H and 78 type tubes; and the large dome represented by the 24A and 32 type tubes. These variations in size and/or type of tubes require variations with respect to length, diameter and general contour of the shield forming sections, which changes may be made because they are largely a matter of design. However, certain unintended minor variations in the bulb size 01 a tube of a given type present difiiculties when it is sought to obtain asnug fit, and to compensate for this non-uniformity in bulb size as well as other imperfections, the present invention embodies a simple mechanical expedient which insures sufiicient clearance between the bulb and shield-forming parts to obtain always a close fit therebetween.

This may be accomplished by providing circumferentially inwardly formed grooves 9 and I located near the top and bottom respectively of the shield members. The depth of the grooves 9 and H3 is sufiicient to prove a two point or line contact between the outer wall of the bulb 5 and the inner surface of the shield sections l and 2 at the points of engagement with the ribs formed by making the grooves. That is to say, there is thus provided sufiicient clearance between the inner walls of the shield parts and the outer wall of the tube so that the only points of contact between the shield members and the tube elements are where said ribs engage with the tube parts. This construction not only compensates for any variation in bulb size that would have a tendency to cause the shield halves I and 2 to fit the tube poorly, but also compensates for manufacturing imperfections such as crooked bases, i. e., bases imperfectly aligned with respect to the longitudinal axis of the bulb, etc. 7

The method of connecting the shield to a source of ground may be of any convenient form such as a spring clip, wire or the like. Since the manner or method of making this connection is-well understood to those skilled in the art it has not been illustrated. Further, as no point has been made of the kind of material from which the shield is to be constructed, it may be assumed to be either magnetic or nonmagnetic material.

Although the invention has been described in its preferred form, modifications thereof will suggest themselves to those skilled in the art, but it is desired to cover all such modifications as may come within the scope of the appended claims.

What is claimed is:

1. A conductive shield for electrostatically screening the electrode system of a radio tube from external electrical disturbances comprising a pair of substantially similar dished metal members having a length sufiicient to enclose the tube to be housed therein when measured from substantially the lower edge of the base to slightly above the end of the top terminal of the tube, the top part of said members surrounding said top terminal being substantially smaller in diameter than the remainder of the shield but substantially larger in diameter than the top terminal, one of said metal members being provided with an aperture originating at the perimetral edge of its top portion and extending downwardly a distance suf ficient to insure clearance toa leading-in conductor for making electrical connection with the top terminal of the tube, and resilient means for maintaining said metal shield members in an assembled position, said shield members having peripherally extending channels or beads in the upper and lower portions thereof.

2. A form-fitting tube shield comprised of twosymmetrical paired parts formed from sheet metal, said parts forming when assembled so that the longitudinal edges the other, a hollow casing for the tube, said cas ing comprising a bulbous section having an inner contour substantially conforming to the outer contour of the bulb, a dome section adjacent thereto having an inner contour substantially conforming to the outer contour of the dome portion of the tube, and contiguous with said dome portion a chimney portion adapted to surround the top cap of the tube, said chimney being substantially smaller in diameter than the shield body yet substantially larger in diameter than the top cap of the bulb, said chimney portion being provided with a cut-away portion to permit the introduction of a leading-in conductor, and resilient means for maintaining said shield members in an assembled position, said shield parts having peripherally extending channels or beads in the upper and lower portions thereof.

3. A conductive shield for a radio tube of the type having a base sealed to one end of the glass bulb and an electrode sealed to the other end of the bulb, opposite to the base, said electrode being provided with a top cap extending in alignment with the longitudinal axis of the tube, said shield being adapted to electrostatically screen the electrode system of said radio tube from external electrical disturbances comprising a pair of thin sheet metal members, each having a length substantially equal to the space measured from substantially the lower edge of the base to slightly above the end of the top cap of the tube, the inner contour of each of said members conforming substantially to the outer contour of one-half of the bulb, said members forming, when assembled with the longitudinal edges of one abutting those of the other, a casing having substantially the configuration f the bulb, the upper part of each shield member having a semi-cylindrical extenstion, said semi-cylindrical extensions being adapted to form a chimney surrounding the top of one part abut those of cap of the bulb, said chimney being substantially smaller in diameter than the shield body yet substantially larger in diameter than the top cap of the bulb, a cutaway portion in said chimney suit- 5 able for permitting an electrical conductor to be attached to the top cap when the shield is in an assembled position, and a clamping ring seated in a circumferentially formed groove in the external surface of said shield members for maintaining 1O them in an assembled position, said shield members having peripherally extending channels or beads in the upper and lower portions thereof.

4. A form-fitting tube shield comprised of two symmetrical paired parts formed from sheet metal, said parts forming when assembled so that the longitudinal edges of one part abut those of the other, a hollow casing for the tube, said casing comprising a bulbous section having an inner contour substantially conforming to the outer contour of the bulb, a dome section adjacent thereto having an inner contour substantially conforming to the outer contour of the dome portion of the tube, and contiguous with said dome portion a chimney portion adapted to surround the top cap of the tube, said chimney portion being provided with a cut-away portion to permit the introduction of a leading-in conductor, said shield members having sets of aligned semi-circular grooves formed on their surfaces, 39 one set of said grooves being located adjacent the base of the tube, another set of said grooves being located at the dome section of the tube, said grooves forming internal ribs adapted to function as points of contact for the shield members with the tube, whereby variation in the bulb or imperfections in joining it to the base of the tube are compensated for with respect to the shield fitting the tube properly.

5. A form-fitting tube shield comprising a 40 plurality of sections formed from sheet metal,

said sections being adapted to be assembled with their longitudinal edges in engagement to form a hollow casing for a tube, said casing comprising a bulbous section having an inner contour substantially conforming to the outer contour of the 5 tube, a dome section adjacent thereto having an inner contour substantially conforming to the outer contour of the dome portion of the tube, said shield sections having sets of indentations formed on their surfaces, one set of indentations 10 being located adjacent the base of the tube, another set of said indentations being located at the dome portion of the tube, said indentations acting as bearing points for contact of the shield sections with the tube. 15

6. A form-fitting shield for radio tubes, said shield comprising a plurality of longitudinal sections adapted to mate at the edges extending longitudinally of the tube and when assembled to assume a configuration generally resembling 20 that of the tube, the girth of said shield being slightly larger than that of the tube, means to hold the sections in assembled relation about the tube, and indentations spaced from said means on said sections adapted to act as bearing points 2 for contact of the sections with the tube.

'7. A form-fitting tube shield comprising a plurality of sections formed from sheet metal, said sections being adapted to be assembled with their longitudinal edges in engagement to form a hollow casing for a tube, said casing comprising bulbous and dome portions having an inner contour substantially conforming to the outer contour of the tube, said shield sections having peripherally extending channels or beads in the upper and lower portions thereof, and means to hold the sections in assembled relation about the tube.

FREDERICK HAFECOST. EDWARD F. STAVER. 

